Device for producing mechanical force by pressure of a fluid

ABSTRACT

In a device for the production of pressure by means of a piston (2), the piston (2) which has a rectangular cross-section is arranged in a cylinder (1) whose cylinder bore has also a rectangular cross-section. A cylindrical sleeve (3) is arranged inside the cylinder (1) and its edges rest tightly against two parallel surfaces (11, 12) located opposite each other. When a pressure agent is led into the interior of the sleeve (3) over a cylinder wall (9), the sleeve (3) pushes the piston (2) with a high pressure out of the cylinder block.

This is a division of application Ser. No. 563,412, filed 11/29/83, nowU.S. Pat. No. 4,543,877.

The invention concerns a device for the production of pressure by meansof an elastic component on which a pressure agent can act and which isarranged between two parts movable relatively towards each other.

Customarily, pressure cylinders are used for the production of pressurewhich consist of a circular-cylindrical block and a piston moving in it.A connecting borehole ends in the interior of the cylinder for thesupply and discharge of a pressure agent, for example, compressed air orhydraulic fluid. Gasket rings are arranged between the cylinder wall andthe piston in order to prevent escape of pressure medium between thecylinder wall and the piston. A proper sealing between the piston andthe cylinder wall is practically only possible when the piston and thecylinder bore have a circular cross-section.

In this instance, the piston pressure is dependent on the pressure ofthe pressure agent and on the piston surface. Since the pressure of thepressure agent is usually limited, it is necessary to design the pistonsurface as large as possible for high piston pressures which leads tocylinders with a large diameter whose installation often causesdifficulties. Another difficulty of a large piston diameter is to beseen in the fact that the guiding of the piston in the cylinder and thesealing between the piston and the cylinder wall becomes problematic. Inorder to avoid the disadvantage of a large piston diameter, it is knownto use stepped cylinders. However, they have a complicated structureand, therefore, they are expensive. Another disadvantage is to be seenin its relatively great structural length. Furthermore, it is known tohave the piston act on a toggle lever mechanism for the production of ahigher pressure than the operating pressure. This structure is alsorelatively complex and has additionally the disadvantage that it may notbe possible to use it depending on the installation conditions. Thedescribed problems occur particularly with operating cylinders which areused for punching, pressing, cutting and stamping where the cylindersmust produce high operating pressures with a relatively small stroke.

Additionally, flexible pressure vessels are known in the form ofcompressed air cushions. This is a question of oblong or round flatvessels of an elastic material which have a compressed air connectionleading into the interior of the vessel. When these compressed aircushions are arranged between a rigid stop and a piston, then it ispossible to perform cutting and reforming operations or similar ones ordirect clamping operations, etc. using subsequent tools with the actionof the compressed air on the compressed air cushions. Such compressedair cushions can also be arranged one after the other in order toincrease the stroke of the piston. These compressed air cushions have anumber of advantages in comparison with the aforementioned pressurecylinders. They exert, for example, a continuous area pressure which ismore favorable for many cases of application than the almostpoint-shaped pressure exerted by a conventional piston.

The disadvantage is here that the compressed air cushions are relativelyexpensive since they must sustain a many times higher bursting pressurein comparison with the operating pressure for safety reasons.Furthermore, it is disadvantageous that they are sensitive to sharpedges and objects with sharp edges since they can damage the walls ofthe cushion. Also, their age resistance is negatively influencedparticularly in an oxidizing atmosphere and under the effect of UVradiation.

It is the task to improve the device of the kind mentioned in theintroduction in such a way that the elastic component can be designed ina simple form and, when the pressure acts on it, it rests in a casingwhich supports it all around and at least one of the supporting surfacescan be designed as an actuating element for the movable part of thedevice effecting the pressure action.

This task is accomplished with the characterizing features of claim 1.Advantageous further developments can be taken from the sub-claims.

A very simple design of the elastic component is given in anadvantageous manner by this structure which, in principle, has thesimple shape of a cylinder which is placed simply into the approximatelyquadrangle-shaped interior of a casing of the device with its axisdiagonal to the pressure direction of the movable part. However, theelastic component may also have just the shape of a belt whose ends arefastened, depending on the design of the device, in a suitable manner sothat a belt loop is obtained which will still be further explained.

The elastic components or the sleeve itself does not require aconnecting nipple in this instance for the pressure agent supply whichis effected through an opening in one of the walls of the casing againstwhich one of the edges of the opening of the sleeve rests.

Since the sleeve is supported all around by walls, it must not be fullydimensioned or over-dimensioned with regard to the pressure load but itmust only meet the expansion loads which can be determined without anydifficulty.

Furthermore, the design of the device and particularly the sleeve whichis open on both sides result in an advantageous and preferredpossibility of a further development to the effect that the sleeve canserve as a drive for a toggle lever mechanism which is thusself-integrated into the device in an advantageous manner and which willstill be explained.

Exemplified embodiments will be further explained below with the help ofthe drawings. There are shown:

FIG. 1 a longitudinal cross-section through the left half of the firstdesign;

FIG. 2 a longitudinal cross-section through the right portion of anotherdesign;

FIG. 3 a cross-section along the line III--III in FIG. 2;

FIG. 4 a longitudinal cross-section through a clamping cylinder notbeing acted upon;

FIG. 5 a longitudinal cross-section through the left portion of thecylinder according to FIG. 4 being acted upon;

FIG. 6 a cross-section along the line VI--VI in FIG. 4;

FIG. 7 a longitudinal cross-section through an operating cylinger withtwo toggle level mechanisms;

FIG. 8 a cross-section along the line VIII--VIII in FIG. 7;

FIG. 9 a longitudinal cross-section through an operating cylinder with aspring mechanism and

FIG. 10 a cross-section along the line X--X in FIG. 9.

The piston 2 which is rectangular in its cross-section is arranged in acup-shaped cylinder 1 which has also a rectangular cross-section.

The casing of the cylinder 1 consists of a lower side 8 from which twowalls 9, 10 go off at a right angle. Their surfaces 11, 12 which aredirected towards each other are plane and run in parallel towards eachother. The piston 2 moves between these surfaces 11, 12. The casing ofthe cylinder 1 has two additional walls 13, 14 at a right angle to thewalls 9, 10 and at a right angle to the lower side 8 between which thepiston 2 is arranged with a certain play.

The piston 2 is provided with an oblong recess 15 on its lower sidewhich has a U-shape in longitudinal direction and is open towards thelower side 8 of the cylinder 1. An elastic O-shaped sleeve 3 is arrangedin this recess 15 which rests at the bottom against the lower side 8 ofthe cylinder 1. This sleeve 3 has sealing lips 16 which are directedinto the interior 7 of the sleeve 3 and rest against the surfaces 11,12. The wall 9 is provided with a connecting borehole 17 whichcommunicates with the interior of the sleeve 3.

In the case of the exemplified embodiment according to FIG. 1, it is aquestion of a cylindrical O-shaped sleeve which is round before it isinstalled. However, the sleeve 3' according to FIG. 2 consists of abelt-shaped material. The two ends of this belt-shaped sleeve 3' areconnected with the upper side of the U-shaped recess 15 in a gas andliquid-tight manner in the shown exemplified embodiment using strips 18,18'. However, these ends can also be connected with the lower side 8 ofthe cylinder 1 using the same strips. An adhesive connection would alsobe possible.

Return springs can be provided on both ends of the piston 2 andcylinder 1. Such a design is shown on the left hand side of FIG. 1. Inthis instance, a screw bolt 5 is bolted with the lower side 8 ofcylinder 1. A return spring 4 is arranged in a pocket borehole 19 of thepiston 2 between this pocket borehole 19 and the head 20 of the screwbolt 5 and said return spring 4 pushes the piston 2 into the directionof the lower side 8 of the cylinder 1. The screw bolt 5 is bolted withthe lower side 8 in an adjustable manner whereby the stroke of thepiston 2 can be limited in an adjustable way.

When a pressure agent is pushed through the borehole 17 into theinterior 7 of the sleeve 3 limited by the walls 9, 10, the piston 2executes a stroke movement in the direction of the arrow 21. When theinterior 7 of the sleeve 3 is vented, the piston 2 is returned into itsshown original position by the spring 4.

A block 22 partially filling the interior of the sleeve 3 can bearranged between the two surfaces 11, 12. The clearance volume withinthe sleeve 3 is reduced by this block 22 as it is shown in FIGS. 2 and 3and thus the volume of the pressure agent is reduced accordingly whichmust be introduced into the interior of the sleeve 3 until the strokemovement starts.

The device is distinguished by a rectangular design and the size can beadjusted for the respective purpose of its use. The piston 2 exerts asurface pressure whereby the pressure exerted by the piston 2 is higherin comparison with the pressure of a round cylinder having the samewidth. The height of the device is relatively low in this instance.Since the piston has a play vis-a-vis the walls 13, 14, the piston 2 canadjust to a slightly inclined position of the part upon which it acts.The device is characterized by the use of few individual parts wherebyonly the surfaces 11, 12 must be subjected to fine machining.

The device can be used for many purposes, such as, for example, lifting,clamping, pressing, pushing, stamping, cutting and punching, i.e.particularly there where the piston 2 shall exert a great force or ahigh pressure with a short stroke.

The principle of the use of a sleeve 3 consists of the fact that, withpressure acting on the interior 7 of the sleeve 3, the latter isinclined to adopt a circular shape whereby the piston 2 is moved in thedirection of the arrow 21. With the given exemplified embodiment, thepiston 2 exerts a force when pressure prevails in the interior 7 of thesleeve 3.

FIGS. 4 to 6 show a cylinder which is suitable, in the first place, as aclamping cylinder. In contrast to the example according to FIGS. 1 to 3,the piston 2' exerts a pressure in this instance when the interior 7 ofthe sleeve 3 is not acted upon by the pressure agent.

Those parts in FIGS. 4 to 6 which are the same or equivalent to thoseaccording to FIGS. 1 to 3 are provided with the same reference numbers.

The cylinder 1' which is again rectangular in its cross-section has alower side 8' and the walls 9', 10', 13' and 14'. The piston 2' movesbetween these walls. The sleeve 3 is arranged between the surfaces 11'and 12' of the walls 9' and 10'. The sleeve 3 rests against a stop 23which is fixed to the casing on the side opposite to the lower side 8'.A screw bolt 5' is bolted into this stop 23 which is rigidly connectedwith the casing 1. A return spring 4' is arranged between the bottom ofthe pocket borehole 19' and the head 20' of the screw bolt 5'. Twospring piles 24, 25 are arranged between grooves 26 on the lower side 8'and grooves 27 on the inside of the piston 2'. These spring piles 24, 25consist of springy flat springs, for example, of rolled steel tapematerial. When at rest, they are straight springs as is shown in FIG. 4.When at rest, these spring piles 24, 25 rest against the sleeve 3 andagainst the stop 23.

In the position according to FIG. 4, these spring piles 24, 25 hold thepiston 2' in the shown position. The latter is, therefore, moved out ofthe cylinder 1' and is in a clamping position when the device is used asa clamping cylinder.

When the piston 2' is to be moved into the interior of the cylinder 1',a pressure agent is supplied to the interior 7 of the sleeve 3 wherebythe sleeve 3 pushes the spring piles 24, 25 towards the outside with itsown outer sides as it is shown in FIG. 5. The piston 2' is moved intothe interior of the cylinder 1' by the return spring 4'.

With the position shown in FIG. 4, the piston 2' is suitable to pressagainst any objects and thus to clamp them tightly. When the objectsclamped by the piston 2' shall then be released, a pressure agent is fedinto the interior 7 of the sleeve 3 whereby the piston 2' releases theobject which it has held (FIG. 5).

In the case of the design according to FIGS. 7 and 8, a piston 2" isarranged in the interior of the cylinder 1, being rectangular in itscross-section, which can be moved back and forth. This piston 2" whosecross-section is also rectangular has a piston rod 30 which is guided ina borehole 31 at one end of the cylinder 1. A pressure spring 4" isarranged between this end of the cylinder 1 and the piston 2".

Two knuckle joint mechanisms 32 are provided between the piston 2" andthe lower side 8" of the cylinder 1. These two knuckle joint mechanisms32 rest, on the one hand, against grooves 27' on the piston 2" and, onthe other hand, in grooves 26' on the lower side 8". The two knucklelever joint mechanisms 32 consist each of a first lever 33 and a secondlever 34 whereby the knuckle joint is formed by a wedge-shaped cut onthe lever 34 into which a rounded portion on the lever 33 engages.

The sleeve 3 is arranged between the two joint mechanisms 32, the lowerside 8" and the stop 23' fastened to the casing. This elastic sleeve 3which is annular-shaped when at rest has sealing lips 16 at the insideon its edges which rest against the walls 9, 10 of the cylinder 1running in parallel towards each other. The originally round sleeve 3rest against the joint mechanisms 32 which, when at rest, are bentagainst the sleeve 3.

When the interior 7 of the sleeve 3 is not acted upon by the pressureagent, the spring 4" holds the piston 2", the lever mechanisms 32 andthus the sleeve 3 in the position shown in FIG. 7.

When the interior 7 of the sleeve 3 is acted upon by the pressure agentthrough the connection 17, the inner volume of the sleeve 3 increases.Since the sleeve 3 rests against the stop 23' and against the lower side8", the volume can only increase by moving the areas of the sleeve 3resting against the joint mechanisms 32 laterally towards the outsidewhereby the knuckle joint mechanisms 32 are given an elongated shape. Inthis way, the piston 2" is moved towards the outside out of the cylinder1 with its piston rod 30. When the sleeve 3 is relieved of the pressureagent, the spring 4" returns the piston 2", the lever mechanisms 32 andthe sleeve 3 into the shown initial position.

The stroke movement can be limited by stops 35 in the cylinder chamberwhereby the elongation of the lever mechanisms 32 is limited. Thesestops 35 can be adjustable. They are preferably adjusted in such a waythat a full elongation cannot be achieved so as to guarantee that thespring 4" returns the lever mechanisms 32 into the shown initialposition.

However, a dead center or beyond dead center position which mightpossibly be desired relative to a special clamping problem shall not beexcluded with it. In this instance, the releasing of the beyond deadcenter position can be effected with the help of mechanical means fromoutside or by having a pressure agent act on the knuckle lever partsfrom the outside or such.

The sleeve which consists of an elastic plastic material can have ajacket of spring plate.

The stop 23' on the side of the cylinder chamber is not absolutelynecessary. The sleeve 3 can rest there against the piston 2".

When the inside 7 of the sleeve 3 is acted upon, the piston rod 30performs a relatively slight stroke. However, the piston force is 10 to15 times greater in comparison with a cylinder of the same structuralsize where the inside of the piston 2" is directly acted upon by thepressure agent. This is achieved by the knuckle joint lever mechanisms 4arranged in the interior of the cylinder 1.

The alternative shown in FIGS. 9 and 10 differs from the precedingalternative in the first place in that two curved springs 36 are usedinstead of the knuckle joint mechanisms 32. With the pressure acting onthe inside 7 of the sleeve 3, the sleeve 3 is given an elongated shapewhereby the piston 2" performs a relatively slight stroke with itspiston rod 30 at a high force. In this exemplified embodiment, thesleeve 3 is in contact with the piston 2". In its most simple design,the cylinder may have only one lever mechanism 32 or 26, respectively,for example, the right hand lever mechanism 32 in FIG. 7.

With regard to the designs according to FIGS. 4 to 10, such designs arealso included in which the piston 2 performs a swivel movement relativeto the cylinder 1 and no axial movement. For this purpose, the piston 2is not guided between the walls 13, 14 but, for example, is connected ina joint manner with one of these walls, for example, the wall 14 bymeans of a hinge. Either a spring pile 24 or a flat spring 36 or aknuckle joint mechanism 32 is arranged between the sleeve 3 and theopposite wall 13 and between the lower side 8 of the cylinder 1 and thepiston 2. Thus, the jacket surface of the sleeve 3 is surrounded by thewall 14, the lower side 8, the springs or the knuckle joint mechanismand the piston 2. When pressure acts then on the sleeve 3, the piston 2performs a swivel movement around the hinge owing to the deformation ofthe springs 24 or 36 or the elongation of the knuckle joint mechanism32.

I claim:
 1. A device for producing mechanical force by means of apressure fluid comprising:(a) a cylinder (1) having two side walls (9,10) with surfaces (11, 12) which are plain-parallel to each other andhaving a lower side wall (8) at right angle to said two side walls (9,10); (b) a piston (2) in said cylinder (1) between said two surfaces(11, 12) and guided by said cylinder (1) for movements along said twosurfaces (11, 12); (c) an elastic cylindrical sleeve (3) having twoopening edges, said sleeve being arranged in said cylinder (1) betweensaid lower side wall (8) and said piston (2) with its edges in sealingcontact with said two surfaces (11, 12); (d) at least one bore (17) forsaid pressure fluid in one of said two side walls (9, 10) communicatingwith the interior (7) of said sleeve (3); (e) flat springs (24, 25, 36)being arranged between said lower side wall (8) and said piston (2) andresting against an area of the outer surface of said sleeve (3) todeform said sleeve (3); said flat springs (24, 25, 36) being deformed bysaid sleeve (3) when pressure fluid is supplied in its interior (7)increasing its volume by moving said area laterally towards said flatsprings (24, 25, 36), whereby piston (2) moves as a result of thedeformation of said flat springs (24, 25, 36).
 2. A device as claimed inclaim 1 in which flat springs (36) are arranged on opposite sides ofsaid sleeve (3) which, when the interior (7) of said sleeve (3) is notacted upon by said pressure fluid, are curve-bowed towards each otherand towards said sleeve (3).
 3. A device as claimed in claim 1 in whichflat springs (24, 25) are arranged on opposite sides of said sleeve (3)which, when the interior (7) of said sleeve (3) is not acted upon bysaid pressure fluid, are stretched in a straight line.
 4. A device asclaimed in claim 2 in which grooves (26', 27') are provided on saidlower side wall (8) and on said piston (2) in which the ends of saidflat springs (36) are arranged.
 5. A device as claimed in claim 3 inwhich grooves (26, 27) are provided on said lower side wall (8) and onsaid piston (2) in which the ends of said flat springs (24, 25) arearranged.
 6. A device as claimed in claim 1 in which said sleeve (3) hassealing lips (16) on the open edges.
 7. A device as claimed in claim 1in which at least one return spring (4) is provided between saidcylinder (1) and said piston (2) for moving said piston (2) into saidcylinder (1).
 8. A device as claimed in claim 1 in which a block (22)partially filling the interior (7) of said sleeve (3) is arrangedbetween said parallel surfaces (11, 12) of said cylinder (1).
 9. Adevice as claimed in claim 1 in which a stop (23) is provided in thecylinder (1) between said sleeve (3) and said piston (2).